This invention relates to a developer for electrostatic latent images in electrophotography, electrostatic record or electrostatic printing, more particularly, to a developer that can duplicate images finely, in high quality, and without toner scattering.
As a copying machine for electrophotography has become popular to be used generally, copied images are required to have higher quality and finer reproducibility, mesh pattern reproducibility or half-tone reproducibility than before. It is necessary to use toners with as small size and as sharp distribution as possible in order to meet the requirements. The sharp distribution of particle sizes improves line reproducibility, mesh pattern reproducibility or half-tone reproducibility and the like, and further effects sharp charge-distribution to result in the improvement of image quality such as texture and the like. Techniques that specify the distribution of particle sizes are known in the disclosures of, for example, Japanese patent application of published No. 24369/1982 and Japanese patent application of laid open Nos. 106554/1983, 275766/1986 or 275767/1986 etc.
However, to make particle sizes of toners small results in the decrease of fluidity of toners itself or developers. Therefore, it is desirable to make toners spherical as well as to make particle sizes of toners small in order to prevent the decrease of fluidity of toners or developers.
When toners are made spherical, there arise other problems such as low contact-possibility and low chargeability because of the spherical shapes. That is, the use of ferrite type carriers which are used generally for toners of small sizes or spherical toners results in the formation of copied images with many fogs on account of poor electrification-build-up, broadening of charge distribution and flying of many toners and the like.